In recent years, as a source of next-generation energy, various fuel cell devices have been proposed in which a cell stack device formed by electrically connecting a plurality of solid oxide fuel cells (hereinafter, may be abbreviated to fuel cell) in series is housed in a housing container.
The fuel cells of such fuel cell devices are provided with a conductive supporting body containing Ni and this conductive supporting body has a pair of main surfaces parallel to each other and a fuel gas passage for circulating fuel gas therein. Then, a fuel cell formed by laminating a fuel electrode layer, a solid electrolyte layer, and an oxygen electrode layer in order on the first main surface of the conductive supporting body and laminating an interconnector layer on the second main surface has been proposed (for example, refer to Patent Literature 1).
The fuel cell of Patent Literature 1 is configured by bonding both ends of a solid electrolyte layer, which is formed of a dense zirconia, formed so as to surround the periphery of a hollow, plate-shaped conductive supporting body, with both ends of an interconnector layer formed of dense lanthanum chromite.
That is, the fuel cell of Patent Literature 1 is configured such that the periphery of the conductive supporting body is hermetically surrounded by the solid electrolyte layer and the interconnector layer and the fuel gas which passes through the interior of the conductive supporting body does not leak out to the outside from the dense tubular body formed by the solid electrolyte layer and the interconnector layer.
In order to prevent cracks in such a dense tubular body, a fuel cell with a so-called dumbbell shape where both ends in the width direction of the fuel cell are bulged in the thickness direction is known in the conventional art (for example, refer to Patent Literature 2).
Patent Literature 2 discloses a fuel cell with a shape where each side in the width direction of a flat section are bulged in the thickness direction, in which, when the thicknesses of the conductive supporting body, the inner electrode layer, and the solid electrolyte layer corresponding to the flat section are respectively L1, M1, and N1 and the thicknesses of the conductive supporting body, the inner electrode layer, and the solid electrolyte layer corresponding to the ends are respectively L2, M2, and N2, a relationship of 1.01≤(L2+M2+N2)/(L1+M1+N1)≤1.3 is satisfied.